A review on refractance window drying process of fruits and vegetables: its integration with renewable energies

Abstract

Drying is a fundamental process in the food industry, especially for highly perishable foods, such as fruits and vegetables, because they tend to have short durability post-harvest, resulting in economic and environmental losses. The Refractance Window (RW) is a suitable technique for fruits and vegetables as it maintains the nutritional quality of the raw material in the dry product. Although RW is more energy-efficient than hot air-based techniques, the equipment traditionally consumes electricity, largely obtained from fossil fuels, emitting polluting gases. As a solution to this problem, hybridization of the heating system can be adopted in the drying process. Hybridization is when two or more heat transfer techniques are used in food dehydration. Renewable alternatives, such as solar energy, represents a clean and abundant energy source. The integration of these technologies (RW with solar energy) represents a technological improvement for the food industry, especially regarding environmental concerns. The present study analyzed the current progress in the integration of renewable energies into traditional RW for the drying of fruits and vegetables, as well as highlighted the existing knowledge gaps.

Keywords:
Cast-tape drying; Food quality; Hybrid drying; Conventional drying; Renewable energy; Non-renewable energy

HIGHLIGHTS

The RW is a suitable technique for drying fruits and vegetables

The use of solar energy in a hybrid form with electricity reduces costs and possible environmental impacts

Compared to conventional techniques, the RW is more energy efficient

Bioactive retention is more effective compared to freeze-dried material